A spark plug includes a center electrode assembled to a metal shell via an insulator. In this assembly, for example, an annular ring member is disposed between an outer peripheral surface of the insulator and an inner peripheral surface of the metal shell, and powder for sealing (for example, talc of powder) is filled between the outer peripheral surface and the inner peripheral surface (for example, see JP-A-2000-215964 (Patent Document 1) and JP-A-2006-66385 (Patent Document 2)). Thus, the ring member and the powder disposed between the insulator and the metal shell seal between the insulator and the metal shell. Furthermore, the ring member and the powder improve a force of the metal shell to hold the insulator. Consequently, shock of the insulator by an external force applied to the spark plug (for example, a vibration due to abnormal combustion such as knocking) is suppressed. This allows reduction in damage to the insulator.